Quick answers
- Is CVE-2026-48851 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-48851 being exploited in the wild.
- How severe is CVE-2026-48851?
- Low severity, with a CVSS score of 3.1, published 25 May 2026.
- Which products and versions are affected?
- Putty 0.77 to 0.83.
- Is there a fix for CVE-2026-48851?
- A patch was published on 2026-05-22: PuTTY 0.84 released with a fix. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-48851 attacked?
- It is attacked over the network, in a network appliance.
- Am I affected by CVE-2026-48851?
- Check whether you run Putty at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A vulnerability exists in PuTTY versions 0.77 through 0.83 due to improper state management of the 'trust sigil' (a UI indicator used to distinguish client-side prompts from server-sent data). When connecting via a proxy that requires authentication, PuTTY enables the trust sigil for its internal prompts but fails to clear this status before transitioning to the main Telnet or Rlogin session. An attacker controlling a malicious server or performing a Man-in-the-Middle (MITM) attack could exploit this by sending a spoofed password prompt immediately after proxy authentication. Because the trust sigil remains active, the user may be misled into believing the server's prompt is a legitimate request from the PuTTY client. This issue is addressed in version 0.84.
Affected products
- PuTTY PuTTY 0.77 to 0.83
Timeline
- 2026-05-22: patched: PuTTY 0.84 released with a fix.
- 2026-05-25: disclosed: CVE-2026-48851 published.