CVE-2021-27137

Published Jul 16, 2026

Last updated 3 months ago

Exploit knownCVSS high 8.1
Ubuntu
Network
Open source
IoT

Overview

Description
An issue was discovered in router/upnp/src/ssdp.c in DD-WRT before 45724. An unsafe strcpy in the UPnP handling functionality allows an unauthenticated remote attacker to send a request that would overflow an internal fixed buffer. Exploitation requires the DD-WRT user to enable UPnP (which is off by default, and only listens on internal interfaces by default). This occurs in ssdp_msearch (reachable by an M-SEARCH request).
Source
cve@mitre.org
NVD status
Analyzed
Products
dd-wrt

Risk scores

CVSS 3.1

Type
Secondary
Base score
8.1
Impact score
5.9
Exploitability score
2.2
Vector string
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity
HIGH

Known exploits

Data from CISA

Vulnerability name
DD-WRT Stack-Based Buffer Overflow Vulnerability
Exploit added on
Jul 21, 2026
Exploit action due
Jul 24, 2026
Required action
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Weaknesses

cve@mitre.org
CWE-121

Social media

Hype score
Not currently trending

  1. 米国サイバーセキュリティ・社会基盤安全保障庁(CISA)が既知の悪用された脆弱性カタログに4件の脆弱性を追加。DD-WRTのCVE-2021-27137、LangflowのCVE-2026-0770、WordPressのCVE-2026-63030とCVE-2026-60137。対処期限は前3件が3日

    @__kokumoto

    21 Jul 2026

    708 Impressions

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  2. 🚨 4 new CISA KEV adds today CVE-2021-27137, CVE-2026-0770, CVE-2026-63030, CVE-2026-60137 https://t.co/0StDFCzdCI #boarnet #cybersecurity #cisakev #cve #threatintelligence #malware

    @boarnetio

    21 Jul 2026

    29 Impressions

    0 Retweets

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    0 Quotes

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. F5 BIG-IP APM Heap-based Buffer Overflow Vulnerability•CVE-2026-94127
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References

Sources include official advisories and independent security research.