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Fencer Intel
critical 9.5

CVE-2026-123870 json

[Eclipse CSI - otterdog] Unauthenticated remote code execution via eval() on format-string-injected webhook body when GITHUB_WEBHOOK_SECRET is unset

published 3d ago modified 3d ago also EUVD-2026-119883 , GHSA-32xf-7j44-xq72

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository eclipse-csi/otterdog. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
9.5
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 23%
public exploits
0
none known

Summary

The otterdog webapp evaluates a format-string built from the incoming GitHub webhook JSON body using Python's eval(). When the GITHUB_WEBHOOK_SECRET configuration value is unset or empty (the code default is None), the HMAC signature check is skipped entirely, allowing an unauthenticated network client to reach the eval() sink with attacker-controlled input and execute arbitrary Python on the webapp host.

Patch / fix

  • Eclipse Foundation otterdog 1.3.2

Is CVE-2026-123870 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 4.0 9.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
CNA 4.0 9.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Inferred packages

No advisory lists a package for this vulnerability yet. The CVE names these as products and links their GitHub repository, and the package registry names the same repository, so they are probably the affected packages. Low confidence: the versions are the CVE’s own for the product, and a stack check reports the package as unchecked when there are none.

ecosystem package repository affected
pypi otterdog eclipse-csi/otterdog
>= 0.9.0, < 1.3.2

Affected products

  • Eclipse Foundation otterdog

Classification

Weakness
  • CWE-95 Improper Neutralization of Directives in Dynamically Evaluated Code

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of eclipse-csi/otterdog published their own advisory on GitHub. Reviewed sources take precedence over it.