CVE-2025-26603: heap-use-after-free in function str_to_reg in vim/vim
Description
Vim is a greatly improved version of the good old UNIX editor Vi. Vim allows to redirect screen messages using the `:redir` ex command to register, variables and files. It also allows to show the contents of registers using the `:registers` or `:display` ex command. When redirecting the output of `:display` to a register, Vim will free the register content before storing the new content in the register. Now when redirecting the `:display` command to a register that is being displayed, Vim will free the content while shortly afterwards trying to access it, which leads to a use-after-free. Vim pre 9.1.1115 checks in the ex_display() function, that it does not try to redirect to a register while displaying this register at the same time. However this check is not complete, and so Vim does not check the `+` and `*` registers (which typically donate the X11/clipboard registers, and when a clipboard connection is not possible will fall back to use register 0 instead. In Patch 9.1.1115 Vim will therefore skip outputting to register zero when trying to redirect to the clipboard registers `*` or `+`. Users are advised to upgrade. There are no known workarounds for this vulnerability.
Classification
CVE ID: CVE-2025-26603
CVSS Base Severity: MEDIUM
CVSS Base Score: 4.2
CVSS Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:L
Affected Products
Vendor: vim
Product: vim
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.02% (probability of being exploited)
EPSS Percentile: 1.79% (scored less or equal to compared to others)
EPSS Date: 2025-03-19 (when was this score calculated)
References
https://github.com/vim/vim/security/advisories/GHSA-63p5-mwg2-787vhttps://github.com/vim/vim/commit/c0f0e2380e5954f4a52a131bf6b8