January, the media proxy/embed service of stoatchat (stoatchat/stoatchat), before version 0.15.5…

Why it is Amber

• CVSS 8.2 high
• Remotely exploitable without logging in

References

• https://github.com/stoatchat/stoatchat/security/advisories/GHSA-qv38-hwhv-jm49
• https://www.vulncheck.com/advisories/stoatchat-before-0.15.5-local-filesystem-read-via-svg
• https://github.com/stoatchat/stoatchat/security/advisories/GHSA-qv38-hwhv-jm49

Original description

January, the media proxy/embed service of stoatchat (stoatchat/stoatchat), before version 0.15.5 improperly resolves SVG <image href> values as local filesystem paths when a fetched resource is served as image/svg+xml. An unauthenticated remote attacker who causes the service to proxy an attacker-hosted SVG (e.g. via the /proxy endpoint) can determine whether local files exist through observable response-time differences, and can cause supported local image files to be disclosed after re-encoding. Because each referenced file is read in full with no effective limit on the number or total volume of reads, a single request can also generate an unbounded amount of local filesystem I/O and memory pressure (the published proof of concept drives about 4.34 GB of reads), leading to denial of service. The issue is fixed in 0.15.5.