CVE-2026-90829: GNU Binutils Use-After-Free Vulnerability

CVE-2026-90829 Overview

CVE-2026-90829 is a null pointer dereference vulnerability in GNU Binutils version 2.47. The flaw resides in the bfd_elf_set_group_contents function within bfd/elf.c, which handles SHT_GROUP section processing in ELF binaries. An attacker with local access can trigger the dereference by supplying a crafted ELF object that manipulates group section contents. Successful exploitation causes the affected Binutils tool to crash, producing a denial-of-service condition. The issue is tracked under [CWE-404: Improper Resource Shutdown or Release]. Public disclosure occurred through VulDB and a Sourceware bug report, and the upstream project had not responded at the time of publication.

Critical Impact
Local attackers can crash Binutils utilities by processing a malicious ELF file, disrupting build pipelines and analysis workflows that depend on tools such as ld, objcopy, and objdump.

Affected Products

GNU Binutils 2.47
Downstream toolchains bundling the affected bfd library
Build and analysis pipelines invoking ld, objcopy, or objdump on untrusted ELF inputs

Discovery Timeline

2026-09-14 - CVE-2026-90829 published to the National Vulnerability Database
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-90829

Vulnerability Analysis

The vulnerability affects bfd_elf_set_group_contents, a routine in the Binary File Descriptor (BFD) library responsible for populating the contents of ELF SHT_GROUP sections. When Binutils processes a crafted ELF file containing malformed group section metadata, the function dereferences a pointer that has not been validated for nullity. The resulting segmentation fault terminates the running Binutils utility.

The attack requires local access and low privileges. Impact is limited to availability of the tool processing the file, with no direct memory corruption or code execution reported. Details are documented in the Sourceware Bug Report and cataloged in VulDB CVE-2026-90829.

Root Cause

The root cause is missing null-pointer validation on a structure returned during SHT_GROUP section handling inside bfd/elf.c. When the ELF input specifies group members that resolve to a null section reference, the function proceeds to write to an invalid address. This aligns with [CWE-404], where a resource is accessed after an expected initialization step has failed silently.

Attack Vector

Exploitation requires an attacker with local access to place a malicious ELF file where a privileged or automated Binutils invocation will process it. Common scenarios include continuous integration systems that link or inspect artifacts contributed by lower-privilege users, or shared multi-user development hosts. Because the crash occurs during parsing, no execution of the ELF binary itself is required — invoking ld, objdump, or similar tools is sufficient to trigger the dereference.

A proof-of-concept ELF sample is referenced in the Sourceware bug attachment. No working exploitation code that achieves privilege escalation or memory corruption has been published.

Detection Methods for CVE-2026-90829

Indicators of Compromise

Unexpected segmentation faults or SIGSEGV core dumps produced by ld, objcopy, objdump, or other Binutils tools
Build pipeline failures correlated with newly introduced or externally sourced ELF object files
Presence of ELF files with malformed SHT_GROUP section headers in developer or artifact directories

Detection Strategies

Scan ELF inputs with a validator that inspects SHT_GROUP section entries for unresolved section references prior to invoking Binutils
Enable crash reporting on build agents to capture stack traces referencing bfd_elf_set_group_contents
Monitor process exit codes from Binutils invocations in CI/CD systems and alert on non-zero termination correlated with signal 11

Monitoring Recommendations

Aggregate build-host crash telemetry and correlate it with the specific object files being processed at the time of failure
Track Binutils package versions across developer workstations and build infrastructure to identify systems running the affected 2.47 release
Retain crash dumps in a centralized data lake for after-the-fact triage when malformed ELF inputs are suspected

How to Mitigate CVE-2026-90829

Immediate Actions Required

Inventory hosts and containers running GNU Binutils 2.47 and prioritize build servers that ingest untrusted ELF input
Restrict which users and pipeline jobs can supply ELF files to privileged Binutils invocations
Route Binutils execution on untrusted input through sandboxed or containerized environments with strict resource limits

Patch Information

At the time of publication, the GNU Binutils project had not issued a fix. Track the Sourceware Bug Report #34451 for upstream patch progress and monitor the GNU Binutils project for release announcements. Downstream Linux distributions may issue backported fixes ahead of an upstream release; consult the appropriate vendor security advisories.

Workarounds

Pin build pipelines to a prior Binutils release that does not exhibit the crash while awaiting an upstream fix
Pre-validate ELF inputs with an independent parser to reject files with malformed SHT_GROUP sections before Binutils processes them
Isolate Binutils invocations in ephemeral containers so a crash does not disrupt the host or leak partial build state

bash

# Identify Binutils versions across managed hosts
ld --version | head -n 1

# Restrict Binutils execution on untrusted input to a sandboxed user
sudo -u builduser --preserve-env=PATH \
  systemd-run --scope --uid=builduser \
  --property=MemoryMax=512M --property=TasksMax=64 \
  /usr/bin/objdump -h /path/to/untrusted.o