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CVE-2026-17556: A path traversal vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated atta

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CRITICAL 9.1REMOTEUPGRADE

CVE-2026-17556 is a critical-severity flaw (CVSS 9.1) affecting enterprise server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A path traversal vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to delete arbitrary files and directories on the instance, including the entire user storage directory containing Git LFS objects, release assets, attachments, and avatars. The X-GitHub-Request-Id request header was used without sanitization as a filesystem path segment for the upload buffer directory, so a traversal value pointed th

Why this priority

  • Critical severity
  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score9.1 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance0.8% (top 44%)
CISA exploited listNo
WeaknessCWE-22
Published2026-08-05
Last modified2026-10-23
Publisher (CNA): GitHub, Inc. (Products Only) · Vendor: github

Am I affected?

Timeline

github enterprise server UPGRADE
Affected: < 3.17.19 · >= 3.18.0 and < 3.18.13 · >= 3.19.0 and < 3.19.10 · >= 3.20.0 and < 3.20.6 · >= 3.21.0 and < 3.21.4
Fixed in: 3.17.19, 3.18.13, 3.19.10, 3.20.6, 3.21.4
Safe to downgrade to: a release before 3.18.0
1. Check installed version
apt-cache policy enterprise-server || rpm -q enterprise-server || enterprise-server --version
2. UPGRADE to 3.17.19 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade enterprise-server
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade enterprise-server
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 3.18.0 (Debian / Ubuntu)
apt-cache madison enterprise-server sudo apt install enterprise-server=<VERSION_BEFORE_3.18.0> sudo apt-mark hold enterprise-server
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list enterprise-server sudo dnf downgrade enterprise-server-<VERSION_BEFORE_3.18.0> sudo dnf versionlock add enterprise-server
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Fedora 46 · python-openslide · FIXED · 1.4.7-1.fc46 · FEDORA-2026-336bea884e · source
sudo dnf upgrade --advisory=FEDORA-2026-336bea884e
Fedora ELN · valgrind · FIXED · 3.28.0-1.eln159 · FEDORA-2026-c593ef1d15 · source
sudo dnf upgrade --advisory=FEDORA-2026-c593ef1d15
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-17556?

enterprise server: upgrade to 3.17.19, 3.18.13, 3.19.10, 3.20.6, 3.21.4. Exact commands for each OS are on this page.

Is CVE-2026-17556 being exploited?

CVE-2026-17556 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-17556 affect?

CVE-2026-17556 affects enterprise server. Severity is critical (CVSS 9.1). A path traversal vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to delete arbitrary files and directories on the instance, including the entire user storage directory containing Git LFS obj

How urgent is CVE-2026-17556?

Priority 51/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

GitHub vulnerabilities · Git vulnerabilities

Related CVEs

References

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