CVE-2026-3888

Published Mar 17, 2026

Last updated 5 months ago

CVSS high 7.8
Ubuntu

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-3888 is a local privilege escalation vulnerability found in snapd on Linux systems. This flaw allows an unprivileged local attacker to gain root privileges. The vulnerability stems from an unintended interaction between two standard system components: `snap-confine`, which manages execution environments for snap applications, and `systemd-tmpfiles`, responsible for cleaning up temporary files and directories. Specifically, the issue occurs when `systemd-tmpfiles` is configured to automatically clean up snap's private `/tmp` directory. An attacker can exploit a race condition during this cleanup process to re-create the directory with malicious permissions or content before `snap-confine` utilizes it. While the exploit requires a specific time-based window, typically between 10 and 30 days, it can lead to a complete compromise of the host system. This vulnerability affects various Ubuntu versions, including 16.04 LTS, 18.04 LTS, 20.04 LTS, 22.04 LTS, and 24.04 LTS.

Description
Local privilege escalation in snapd on Linux allows local attackers to get root privilege by re-creating snap's private /tmp directory when systemd-tmpfiles is configured to automatically clean up this directory. This issue affects Ubuntu 16.04 LTS, 18.04 LTS, 20.04 LTS, 22.04 LTS, and 24.04 LTS.
Source
security@ubuntu.com
NVD status
Analyzed
Products
ubuntu_linux

Risk scores

CVSS 3.1

Type
Secondary
Base score
7.8
Impact score
6
Exploitability score
1.1
Vector string
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Severity
HIGH

Weaknesses

security@ubuntu.com
CWE-268

Social media

Hype score
Not currently trending

  1. Nginx-UIdeki yedekleme sızıntısından root kabuğuna uzanan CVE-2026-3888 ve Snap Copy-Fail root açığı CVE-2026-27944 - yarın detayları paylaşıyoruz. Takipte kalın. https://t.co/2SElhCfANS

    @r3csec

    20 May 2026

    0 Impressions

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  2. NEW Videoo: CVE-2026-3888: Nginx-UI Backup Leak to Root Shell + CVE-2026-27944 Snap Copy-Fail Root New video covering a full Linux exploitation chain: Unauth API → Backup leak → Credential cracking → SSH → Snapd TOCTOU privesc → Root shell https://t.co/VjCTRiQlpy

    @NullSecurityX

    13 May 2026

    5208 Impressions

    13 Retweets

    45 Likes

    22 Bookmarks

    1 Reply

    1 Quote

  3. Sorry everyone, I'm late (again) as I was taking the OSCP ! New HackTheBox walkthrough: Snapped Nginx UI CVE-2026-27944 backup extraction → bcrypt cracking → dual privesc paths (snap CVE-2026-3888 + kernel copy-fail CVE-2026-31431). Enjoy the video! https://t.co/23iQXDMVZ

    @Strikoder

    11 May 2026

    3 Impressions

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  4. Top 5 Trending CVEs: 1 - CVE-2026-25253 2 - CVE-2026-3888 3 - CVE-2026-40372 4 - CVE-2025-59536 5 - CVE-2026-26144 #cve #cvetrends #cveshield #cybersecurity https://t.co/4Fua3CAN6W

    @CVEShield

    23 Apr 2026

    194 Impressions

    0 Retweets

    1 Like

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  5. Top 5 Trending CVEs: 1 - CVE-2026-3888 2 - CVE-2025-31277 3 - CVE-2025-55182 4 - CVE-2026-20643 5 - CVE-2026-32746 #cve #cvetrends #cveshield #cybersecurity https://t.co/4Fua3CAN6W

    @CVEShield

    19 Mar 2026

    155 Impressions

    0 Retweets

    0 Likes

    1 Bookmark

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Configurations

Related CVEs

  1. Issue summary: The DTLS retransmission logic does not correctly handle a handshake message write that is suspended part-way through. The retransmitted message can be read past the message buffer and the retransmission overwrites the internal state the suspended write needs to resume correctly. Impact summary: The retransmitted message can disclose a heap memory to the peer as plaintext handshake data or cause a crash and a Denial of Service when the read reaches an unmapped memory region. CWE: CWE-125: Out-of-bounds Read Description: DTLS handshake messages can be written out in multiple fragments, and a write can suspend mid-message (returning WANT_WRITE) if the underlying transport temporarily cannot accept more data. While such a write is suspended, the DTLS retransmission timer may independently fire and ask the retransmission logic to resend an earlier, already-acknowledged-as-sent message from its retransmit queue. The retransmission logic reused the same internal buffer and position tracking as the message that was still being written, without resetting the position back to the start of the message being retransmitted. As a result the retransmission was read starting from wherever the suspended write had left off, producing a mislabelled message whose body was leftover bytes from the other, larger message still in flight - content that was never meant to be sent at that point, and which could run past the end of the allocated buffer. Separately, even when the retransmission is positioned correctly, allowing it to run to completion while another write is suspended overwrites the same shared bookkeeping that the suspended write depends on to resume. When the application later resumes the suspended write (via a subsequent SSL_read(), SSL_write(), SSL_accept(), or SSL_connect() call), it finds that bookkeeping in a state inconsistent with the message and aborts the process in a debugging build. The fix resets the retransmission's read position to the start of the message before resending, and skips retransmission entirely whenever a handshake write is still suspended, deferring to the next call that resumes it instead. FIPS impact: no The affected code is outside the FIPS module boundary.•CVE-2026-84782
  2. ZoneMinder versions 1.37.0 before 1.38.0 contain a path traversal vulnerability in the files view that allows authenticated users to read arbitrary files. The path parameter is not properly validated before being passed to output_file, enabling attackers with Events view permission to access sensitive files like configuration files containing database credentials.•CVE-2024-58386
  3. WordPress Core Remote File Inclusion Vulnerability•CVE-2026-87902
  4. Google Chromium V8 Type Confusion Vulnerability•CVE-2026-85046
  5. In the Linux kernel, the following vulnerability has been resolved: net: gro: properly validate BIG TCP aggregation criteria When GRO attempts to aggregate packets beyond GRO_LEGACY_MAX_SIZE (64KB), BIG TCP should only be permitted for plain IPv4 TCP and plain IPv6 TCP (with sufficient MAC header room to insert the temporary HBH jumbo header). However, commit b1a78b9b9886 ("net: add support for ipv4 big tcp") loosened the check in skb_gro_receive(), leading to several issues: 1. skb_gro_receive() checked skb_headroom(p) instead of the actual space before the MAC header (p->mac_header). Because skb_headroom(p) includes mac_len, crafted frames (e.g. injected via AF_PACKET) can pass the check with p->mac_header < 8 bytes. When ipv6_gro_complete() inserts the temporary HBH jumbo header, the memmove() starts before skb->head, causing an out-of-bounds write and wrapping skb->mac_header. 2. It allowed non-IP protocols such as software VLAN (ETH_P_8021Q / ETH_P_8021AD) to aggregate beyond 64KB because p->protocol != ETH_P_IPV6 was true. 3. It checked p->encapsulation instead of NAPI_GRO_CB(skb)->encap_mark, allowing encapsulated flows (e.g. SIT / IPv6-in-IPv4) to aggregate beyond 64KB. Fix skb_gro_receive() to strictly enforce: - NAPI_GRO_CB(skb)->proto == IPPROTO_TCP - Not encapsulated (!NAPI_GRO_CB(skb)->encap_mark && !p->encapsulation) - Protocol must be either ETH_P_IP or ETH_P_IPV6 - If ETH_P_IPV6, p->mac_header must be at least sizeof(struct hop_jumbo_hdr) Returning -E2BIG from skb_gro_receive() ensures that packets which cannot become BIG TCP are cleanly flushed at <= 64KB and delivered intact without dropping. This issue does not exist in mainline (7.0+) because the subsystem was rewritten in commit 81be30c1f5f2 ("net/ipv6: Drop HBH for BIG TCP on RX side"), making this fix relevant only for older stable branches like 6.18.y.•CVE-2026-80725

References

Sources include official advisories and independent security research.