diff --git a/lib/checkbufferoverrun.cpp b/lib/checkbufferoverrun.cpp
index 46d8e1c7c6c..6468d766f93 100644
--- a/lib/checkbufferoverrun.cpp
+++ b/lib/checkbufferoverrun.cpp
@@ -68,7 +68,9 @@ static const ValueFlow::Value *getBufferSizeValue(const Token *tok)
     auto it = std::find_if(tokenValues.cbegin(), tokenValues.cend(), std::mem_fn(&ValueFlow::Value::isBufferSizeValue));
     if (it != tokenValues.cend())
         return &*it;
-    it = std::find_if(tokenValues.cbegin(), tokenValues.cend(), std::mem_fn(&ValueFlow::Value::isContainerSizeValue));
+    it = std::find_if(tokenValues.cbegin(), tokenValues.cend(), [](const ValueFlow::Value& v) {
+        return v.isContainerSizeValue() && !v.isImpossible();
+    });
     return it == tokenValues.cend() ? nullptr : &*it;
 }
 
@@ -588,6 +590,8 @@ ValueFlow::Value CheckBufferOverrunImpl::getBufferSize(const Token *bufTok, cons
                     ValueFlow::Value bufSizeVal;
                     bufSizeVal.valueType = ValueFlow::Value::ValueType::BUFFER_SIZE;
                     bufSizeVal.intvalue = value->intvalue * elementSize;
+                    bufSizeVal.valueKind = value->valueKind;
+                    bufSizeVal.errorPath = value->errorPath;
                     return bufSizeVal;
                 }
             }
@@ -721,7 +725,10 @@ void CheckBufferOverrunImpl::bufferOverflow()
 
 void CheckBufferOverrunImpl::bufferOverflowError(const Token *tok, const ValueFlow::Value *value, Certainty certainty)
 {
-    reportError(getErrorPath(tok, value, "Buffer overrun"), Severity::error, "bufferAccessOutOfBounds", "Buffer is accessed out of bounds: " + (tok ? getRealBufferTok(tok)->expressionString() : "buf"), CWE_BUFFER_OVERRUN, certainty);
+    const auto errorPath = getErrorPath(tok, value, "Buffer overrun");
+    const auto severity = !value || value->isKnown() ? Severity::error : Severity::warning;
+    const std::string msg = "Buffer is accessed out of bounds: " + (tok ? getRealBufferTok(tok)->expressionString() : "buf");
+    reportError(errorPath, severity, "bufferAccessOutOfBounds", msg, CWE_BUFFER_OVERRUN, certainty);
 }
 
 //---------------------------------------------------------------------------
diff --git a/test/testbufferoverrun.cpp b/test/testbufferoverrun.cpp
index 37ab7083902..fa0315f804f 100644
--- a/test/testbufferoverrun.cpp
+++ b/test/testbufferoverrun.cpp
@@ -3564,6 +3564,21 @@ class TestBufferOverrun : public TestFixture {
               "        memset(&a[i], 0, sizeof(a));\n"
               "}\n");
         ASSERT_EQUALS("[test.cpp:4:16]: (error) Buffer is accessed out of bounds: &a[i] [bufferAccessOutOfBounds]\n", errout_str());
+
+        check("void f(const std::vector<uint8_t>& s) {\n" // #14948
+              "    if (s.size() < 4)\n"
+              "        return;\n"
+              "    uint32_t u = 0;\n"
+              "    std::memcpy(&u, &s[0], sizeof(u));\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
+
+        check("void f(const std::vector<uint8_t>& s) {\n"
+              "    if (s.size() == 2) {}\n"
+              "    uint32_t u = 0;\n"
+              "    std::memcpy(&u, &s[0], sizeof(u));\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:4:21]: (warning) Buffer is accessed out of bounds: &s[0] [bufferAccessOutOfBounds]\n", errout_str());
     }
 
     void buffer_overrun_errorpath() {