Saxy's XML encoder writes the target and the content of a processing instruction into the output document verbatim, without validation or…
CVE-2026-66295
Saxy's XML encoder writes the target and the content of a processing instruction into the output document verbatim, without validation or escaping. The encoder builds the construct by concatenating both fields between , so neither field is checked against the constraints the XML specification places on it. Because ?> terminates a processing instruction, a target or content value containing that sequence closes the construct at a position the attacker chooses. Everything the attacker writes after it is emitted as ordinary markup at document level, which allows arbitrary elements, attributes, and further processing instructions to be injected into the serialized document. Appending a matching <? keeps the encoder's own terminator well-formed, so the result still parses and the injection is silent rather than a visible corruption. The target is additionally unconstrained by the XML Name production, which permits injection before the remainder of the processing instruction. The result is XML injection into a serialized document: the tree the application asks Saxy to encode and the tree a downstream parser reads back are no longer the same. Character data, attribute values, and…
Assessment
- CVSS
- 2.1 (v4.0)
- Severity
- Low
- Known exploited
- Not listed in CISA KEV
- Exploit availability
- Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
- Published
- 6 November 2026
- Last updated
- 6 November 2026
- Assigner
- EEF
CVSS vectorCVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N
At the source
References
- https://github.com/qcam/saxy/security/advisories/GHSA-f9r9-vrxq-g566
- https://cna.erlef.org/cves/CVE-2026-66295.html
- https://osv.dev/vulnerability/EEF-CVE-2026-66295
- https://github.com/qcam/saxy/commit/7266632e9407842f28ffac254c56dc41210a5690
- https://github.com/qcam/saxy/commit/4aeb80e2acc318f57bd7453ad2eafd59101a90e0
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