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PatchSiren cyber security CVE debrief

CVE-2026-28525 sbabic CVE debrief

CVE-2026-28525 is an integer underflow vulnerability in the multipart upload parser in mongoose_multipart.c of SWUpdate. This vulnerability allows unauthenticated attackers to cause a denial of service by sending a crafted HTTP POST request to /upload with a malformed multipart boundary and controlled TCP stream timing. The vulnerability is triggered when the buffer length falls within a specific range, causing an out-of-bounds heap read past the allocated receive buffer to a local IPC socket. The CVSS score for this vulnerability is 8.2, indicating a high severity.

Vendor
sbabic
Product
swupdate
CVSS
HIGH 8.2
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-23
Original CVE updated
2026-07-14
Advisory published
2026-04-23
Advisory updated
2026-07-14

Who should care

Users of SWUpdate, particularly those who use it in networked environments, should be aware of this vulnerability. The vulnerability can be exploited by unauthenticated attackers, making it a significant concern for systems that expose SWUpdate to the internet or untrusted networks.

Technical summary

The vulnerability is caused by an integer underflow in the mg_http_multipart_continue_wait_for_chunk() function. This function fails to properly validate the buffer length, leading to an out-of-bounds heap read when the buffer length falls within a specific range. The vulnerability can be exploited by sending a crafted HTTP POST request to /upload with a malformed multipart boundary and controlled TCP stream timing.

Defensive priority

High

Recommended defensive actions

  • Apply the patch: [ref-4](https://github.com/sbabic/swupdate/commit/beee2dc0feef1cfe84f1aa6fc980e104b2e47a74)
  • Refer to the vendor advisory: [ref-5](https://www.vulncheck.com/advisories/swupdate-integer-underflow-in-multipart-upload-parser)

Evidence notes

The vulnerability was reported by [email protected] and is associated with CWE-125 and CWE-191.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-28525 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-28525

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-28525 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-28525

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.