LLVM Security Group Transparency Reports

This page lists the yearly LLVM Security group transparency reports.

2021

The LLVM security group was established on the 10th of July 2020 by the act of the initial commit describing the purpose of the group and the processes it follows. Many of the group’s processes were still not well-defined enough for the group to operate well. Over the course of 2021, the key processes were defined well enough to enable the group to operate reasonably well:

• We defined details on how to report security issues, see this commit on 20th of May 2021

• We refined the nomination process for new group members, see this commit on 30th of July 2021

• We started writing an annual transparency report (you’re reading the 2021 report here).

Over the course of 2021, we had 2 people leave the LLVM Security group and 4 people join.

In 2021, the security group received 13 issue reports that were made publicly visible before 31st of December 2021. The security group judged 2 of these reports to be security issues:

• https://bugs.chromium.org/p/llvm/issues/detail?id=5

• https://bugs.chromium.org/p/llvm/issues/detail?id=11

Both issues were addressed with source changes: #5 in clangd/vscode-clangd, and #11 in llvm-project. No dedicated LLVM release was made for either.

We believe that with the publishing of this first annual transparency report, the security group now has implemented all necessary processes for the group to operate as promised. The group’s processes can be improved further, and we do expect further improvements to get implemented in 2022. Many of the potential improvements end up being discussed on the monthly public call on LLVM’s security group.

2022

In this section we report on the issues the group received in 2022, or on issues that were received earlier, but were disclosed in 2022.

In 2022, the llvm security group received 15 issues that have been disclosed at the time of writing this transparency report.

5 of these were judged to be security issues:

• https://bugs.chromium.org/p/llvm/issues/detail?id=17 reports a miscompile in LLVM that can result in the frame pointer and return address being overwritten. This was fixed.

• https://bugs.chromium.org/p/llvm/issues/detail?id=19 reports a vulnerability in std::filesystem::remove_all in libc++. This was fixed.

• https://bugs.chromium.org/p/llvm/issues/detail?id=23 reports a new Spectre gadget variant that Speculative Load Hardening (SLH) does not mitigate. No extension to SLH was implemented to also mitigate against this variant.

• https://bugs.chromium.org/p/llvm/issues/detail?id=30 reports missing memory safety protection on the (C++) exception handling path. A number of fixes were implemented.

• https://bugs.chromium.org/p/llvm/issues/detail?id=33 reports the RETBLEED vulnerability. The outcome was clang growing a new security hardening feature -mfunction-return=thunk-extern, see https://reviews.llvm.org/D129572.

No dedicated LLVM releases were made for any of the above issues.

2023

In this section we report on the issues the group received in 2023, or on issues that were received earlier, but were disclosed in 2023.

9 of these were judged to be security issues:

https://bugs.chromium.org/p/llvm/issues/detail?id=36 reports the presence of .git folder in https://llvm.org/.git.

https://bugs.chromium.org/p/llvm/issues/detail?id=66 reports the presence of a GitHub Personal Access token in a DockerHub imaage.

https://bugs.chromium.org/p/llvm/issues/detail?id=42 reports a potential gap in the Armv8.1-m BTI protection, involving a combination of large switch statements and __builtin_unreachable() in the default case.

https://bugs.chromium.org/p/llvm/issues/detail?id=43 reports a dependency on an old version of xml2js with a CVE filed against it.

https://bugs.chromium.org/p/llvm/issues/detail?id=45 reports a number of dependencies that have had vulnerabilities reported against them.

https://bugs.chromium.org/p/llvm/issues/detail?id=46 is related to issue 43.

https://bugs.chromium.org/p/llvm/issues/detail?id=48 reports a buffer overflow in std::format from -fexperimental-library.

https://bugs.chromium.org/p/llvm/issues/detail?id=54 reports a memory leak in basic_string move assignment when built with libc++ versions <=6.0 and run against newer libc++ shared/dylibs.

https://bugs.chromium.org/p/llvm/issues/detail?id=56 reports an out of bounds buffer store introduced by LLVM backends, that regressed due to a procedural oversight.

No dedicated LLVM releases were made for any of the above issues.

Over the course of 2023 we had one person join the LLVM Security Group.

2024

Introduction

In the first half of 2024, LLVM used the Chromium issue tracker to enable reporting security issues responsibly. We switched over to using GitHub’s “privately reporting a security vulnerability” workflow in the middle of 2024.

In previous years, our transparency reports were shorter, since the full discussion on a security ticket in the Chromium issue tracker is fully visible once disclosed. This is not the case with issues using GitHub’s security advisory workflow, so instead we give a longer description in this transparency report, to make the relevant information on the ticket publicly available.

This transparency report doesn’t necessarily mention all issues that were deemed duplicates of other issues, or tickets only created to test the bug tracking system.

Security issues fixed under a coordinated disclosure process

This section lists the reported issues where we ended up implementing fixes under a coordinated disclosure process. While we were still using the Chromium issue tracker, we did not write security advisories for such issues. Since we started using the GitHub issues tracker for security issues, we’re now publishing security advisories for those issues at https://github.com/llvm/llvm-security-repo/security/advisories/.

1. “Unexpected behavior when using LTO and branch-protection together”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=58

2. “Security weakness in PCS for CMSE” (CVE-2024-0151)
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=68

3. “CMSE secure state may leak from stack to floating-point registers” (CVE-2024-7883)
   Details are available at GHSA-wh65-j229-6wfp

Supply chain security related issues and project services-related issues

1. “GitHub User Involved in xz backdoor may have attempted to change to clang in order to help hide the exploit”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=71

2. “llvmbot account suspended due to supicious login”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=72

3. “.git Exposure”
   GHSA-mr8r-vvrc-w6rq
   The .git directory was accessible via web browsers under apt.llvm.org, a site used to serve Debian/Ubuntu nightly packages. This issue has been addressed by removing the directory, and is not considered a security issue for the compiler. The .git directory was an artifact of the CI job that maintained the apt website, and was mirroring an open-source project maintained on github (under opencollab/llvm-jenkins.debian.net). The issue is not believed to have leaked any non-public information.

4. “llvm/llvm-project repo potentially vulnerable to GITHUB_TOKEN leaks”
   GHSA-f5xj-84f9-mrw6
   GitHub access tokens were being leaked in artifacts generated by GitHub Actions workflows. The vulnerability was first reported publicly as ArtiPACKED, generally applicable to GitHub projects, leading to an audit of LLVM projects and the reporting of this security issue. LLVM contributors audited the workflows, found that the “release-binaries” workflow was affected, but only exposed tokens that were ephemeral and read-only, so was not deemed a privilege escalation concern. The workflow was fixed in a configuration change as PR 106310. Older exposed tokens all expired, and the issue is closed as resolved.

5. “RCE in Buildkite Pipeline”
   GHSA-2j6q-qcfm-3wcx
   A Buildkite CI pipeline (llvm-project/rust-llvm-integrate-prototype) allowed Remote Code Execution on the CI runner. The pipeline automatically runs a test job when PRs are filed on the rust-lang/rust repo, but those PRs point to user-controlled branches that could be maliciously modified. A security researcher reported the issue, and demonstrated it by modifying build scripts to expose the CI runner’s internal cloud service access tokens. The issue has been addressed with internal configuration changes by owners of the Buildkite pipeline.

Issues deemed to not require coordinated action before disclosing publicly

1. “Clang Address Sanitizer gives False Negative for Array Out of Bounds Compiled with Optimization”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=57

2. “Found exposed .svn folder”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=59

3. “Arbitrary code execution when combining SafeStack + dynamic stack allocations + __builtin_setjmp/longjmp”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=60

4. “RISC-V: Constants are allocated in writeable .sdata section”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=61

5. “Manifest File with Out-of-Date Dependencies with CVEs”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=62

6. “Non-const derived ctor should fail compilation when having a consteval base ctor”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=67

7. “Wrong assembly code generation. Branching to the corrupted “LR”.”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=69

8. “Security bug report”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=70

9. “Using ASan with setuid binaries can lead to arbitrary file write and elevation of privileges”
   Details are available at https://bugs.chromium.org/p/llvm/issues/detail?id=73

10. “Interesting bugs for bool variable in clang projects and aarch64 modes outputting inaccurate results.”
    GHSA-w7qc-292v-5xh6
    The issue reported is on a source code example having undefined behaviour (UB), somewhat similar to this: https://godbolt.org/z/vo4P7bPYr. Therefore, this issue was closed as not a security issue in the compiler.
    As part of the analysis on this issue, it was deemed useful to document this example of UB and similar cases to help users of compilers understand how UB in source code can lead to security issues.
    We concluded that probably the best option to do so is to create a regular public issue at https://github.com/llvm/llvm-project/issues, with the same title as the security issue, and to attach a PDF (which should easily be created using a “print-to-pdf” method in the browser) containing all comments. Such public tickets probably need some consistent way to indicate they come from security issues that after analysis were deemed to be outside the LLVM threat model or weren’t accepted as a needs-resolution-work-in-private security issue for other reasons. The LLVM Security Response group has so far not taken action to progress this idea.
    There was also a suggestion of potentially adding a short section in https://llsoftsec.github.io/llsoftsecbook/#compiler-introduced-security-vulnerabilities that summarizes a short example showing that type aliasing UB can and is causing security vulnerabilities.

11. “llvm-libc qsort can use very large amounts of stack if an attacker can control its input list”
    GHSA-gw5j-473x-p29m
    If the llvm-libc qsort function is used in a context where its input list comes from an attacker, then the attacker can craft a list that causes qsort’s stack usage to be linear in the size of the input array, potentially overflowing the available memory region for the stack.
    After discussion with stakeholders, including maintainers for llvm-libc, the conclusion was that this doesn’t have to be processed as a security issue needing coordinated disclosure. An improvement to qsort’s implementation was implemented through pull request https://github.com/llvm/llvm-project/pull/110849.

12. “VersionFromVCS.cmake may leak secrets in released builds”
    GHSA-rcw6-jqvr-fcrx
    The LLVM build system may leak secrets of VCS configuration into release builds if the user clones the repo with an https link that contains their username and/or password.
    Mitigations were implemented in https://github.com/llvm/llvm-project/pull/105220, https://github.com/llvm/llvm-project/commit/57dc09341e5eef758b1abce78822c51069157869. An issue was raised to suggest one more mitigation to be implemented at https://github.com/llvm/llvm-project/issues/109030.

Invalid issues

The LLVM security group received 5 issues which were created accidentally or were not related to the LLVM project. The subject lines for these were:

• “Found this in my android”

• “[Not a new security issue] Continued discussion for GHSA-w7qc-292v-5xh6”

• “please delete it.”

• “Please help me to delete it.”

• “llvm code being used in malicious hacking of network and children’s devices”

Furthermore, we had 2 tickets that were created to test the setup and workflow as part of migrating to GitHub’s “security advisory”-based reporting:

1. “Test if new draft security advisory gets emailed to LLVM security group”
   GHSA-82m9-xvw3-rvpv

2. “Test that a non-admin can create an advisory (no vulnerability).”
   GHSA-34gr-6c7h-cc93