How severe is CVE-2026-100837?

No CVSS score has been assigned to CVE-2026-100837 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-100837?

CVE-2026-100837 affects the following packages: github.com/edgelesssys/contrast (Go). Ecosystems affected: Go.

How do I fix CVE-2026-100837?

Update github.com/edgelesssys/contrast to 1.21.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-100837 is resolved across your whole dependency graph.

How do I detect CVE-2026-100837 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/edgelesssys/contrast, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-100837 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-100837 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-100837 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-100837?

CVE-2026-100837 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 11th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-100837?

CVE-2026-100837 is classified as CWE-1289 (CWE-1289). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-100837 published, and has it been updated?

CVE-2026-100837 was published on September 27, 2026 and was last updated on October 2, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2026-100837 — contrast

Fix: edgelesssys/contrast@10826b1

CVE-2026-100837 is a CWE-1289 vulnerability in github.com/edgelesssys/contrast. A fix is available for github.com/edgelesssys/contrast — see the affected versions and patch details below.

Edgeless Systems Contrast through 1.20.0 Credential Leak via Registry Suffix Matching

Also known asGHSA-6c87-g9pw-78fxGO-2026-5865

Published

Sep 27, 2026

Updated

Oct 2, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-100837.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs11th percentile — riskier than 11% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹github.com/edgelesssys/contrast

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Config.registryFor selected a per-registry credential / CA / mirror block by checking strings.HasSuffix(name, fqdn) after stripping a single trailing dot. The match has no boundary between the configured FQDN and any preceding characters in the request hostname. A registry configured as [registries."ghcr.io."] is therefore also applied to any image pulled from a host whose name happens to end in the literal byte sequence ghcr.io, including attacker-registered domains such as evilghcr.io. The imagepuller would then send the configured Authorization header (basic auth, registry token, or identity token), trust the configured custom CA bundle, follow the configured mirror, or honour insecure-skip-verify, on requests to that hostname.

Prerequisites

For this to be applicable, an image or layer must be pulled from a "sibling" domain ending in one of the FQDNs configured in the imagepuller config. This may occur due to malicious intent or coincidentally.

Impact

Authentication header leaks to the sibling registry.
If insecure-skip-verify is set on an FQDN, TLS will also not be verified for the sibling registry.
Mirrors configured for an FQDN will also be used with the sibling registry.

Not impacted

Image integrity is not impacted. Image bytes remain pinned by digest in the policy and are validated after the pull. This advisory does not allow code substitution.

Workaround

If possible, configure explicit subdomains in the imagepuller config. A configuration for [registries.".example.registry"] is unaffected, only [registries."example.registry"] is potentially affected.
Audit images and layers configured in the deployment for the existence of sibling domains.

Patches

After this patch, registry matches are determined by exact label equality instead of suffix matching. Each .-separated part of the FQDN must be an exact match with the corresponding label in the image reference.

Severity

AV:N because the leak is over the network to a registry under the attacker's control.
AC:H because exploitation requires the operator to have configured a registry FQDN without a leading . AND the attacker to control a sibling-suffix domain that the deployment will pull from.
PR:N for the eventual recipient.
S:U because impact stays in the imagepuller.
C:L for credential leak (no integrity / availability impact).

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/edgelesssys/contrast`	all versions	1.21.0`go get github.com/edgelesssys/contrast@v1.21.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/edgelesssys/contrast, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/edgelesssys/contrast to 1.21.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-100837 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

# Summary `Config.registryFor` selected a per-registry credential / CA / mirror block by checking `strings.HasSuffix(name, fqdn)` after stripping a single trailing dot. The match has no boundary between the configured FQDN and any preceding characters in the request hostname. A registry configured as `[registries."ghcr.io."]` is therefore also applied to any image pulled from a host whose name happens to end in the literal byte sequence `ghcr.io`, including attacker-registered domains such as `evilghcr.io.` The imagepuller would then send the configured `Authorization` header (basic auth,

O3 Security · Impact-Aware SCA

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